The present invention is concerned with ultraviolet (hereinafter xe2x80x9cUVxe2x80x9d) ray irradiation equipment used for irradiation of untreated water for sterilization, oxidative decomposition of organics, decomposition of harmful substances, etc.
When conventional UV irradiation equipment has been used for an extended period of time for the purpose of removing impurities from untreated water such as sewage, iron and hardness components such as calcium and so forth precipitate on the surface of the UV ray transmission tube(s) surrounding an internal UV ray irradiation lamp(s) since this surface comes in contact with the untreated water. These precipitates obstruct the transmission of UV rays through the UV ray transmission tube(s) surrounding the internal UV ray irradiation lamp(s) and deteriorate the irradiation efficiency thereby degrading the purity of treated water. To cope with the above-mentioned deterioration of UV ray transmission efficiency due to fouling on the surface of the UV ray transmission tube(s), mechanical cleaning means have been employed. In particular, scrapers made of rubber, Teflon and the like have been used to physically clean the surface of the UV ray transmission tube(s). However, this physical method of scraping the surface of the UV ray transmission tube(s) leaves much to be desired as hardness components and other scale deposited on the surface of the UV ray transmission tube(s) usually consist of very fine particles which tend to penetrate into and clog concave pits on the surface, thereby making it difficult to remove such scale by scrapers.
Alternatively, the UV ray transmission tube is immersed in a tank filled with a cleaning solution such as a solution of weak acids, e.g. phosphoric acid, a solution of scale dispersant or the like, thereby removing scale such as hardness components from the surface of the UV ray transmission tube. However, such chemical cleaning of the surface of the UV ray transmission tube has the following drawbacks:
(1) It is cumbersome and time-consuming to disassemble a UV ray transmission tube on the surface of which scale such as hardness components has deposited and to immerse the tube in a cleaning tank.
(2) In order to carry out the above-mentioned cleaning work, ongoing UV irradiation has to be suspended, which in turn results in deterioration of the UV irradiation efficiency.
(3) An excessive quantity of cleaning solution has to be used in the cleaning tank, which entails an expensive cleaning cost.
(4) The cleaning work is not amenable to automation and cannot therefore go with the trend of equipment automation.
Therefore, a need presently exists for a solution to the above-noted problem of UV ray transmission tube fouling which avoids the disadvantages of prior attempted solutions employing mechanical and chemical cleaning of UV transmission tubes.
It is a principal object of this invention to provide novel means for thoroughly washing out from the surface of a UV ray transmission tube those fine particles deposited in concave pits on the tube surface which can not be removed physically by conventional mechanical methods, thereby to keep up the UV transmission efficiency of the UV irradiation tube.
Furthermore, this invention permits achieving the following objectives which cannot be carried out with chemical cleaning using such conventional cleaning solutions such as solutions of weak acids, such as phosphoric acid, and scale dispersants:
(1) in situ scale comprised of hardness components, etc. on a UV ray transmission tube may be easily cleaned off without disassembling the UV ray irradiation unit and taking out the tube fouled with the scale;
(2) UV irradiation efficiency may be maintained without interrupting the UV irradiation for the cleaning work to remove scale deposited on the UV transmission tube;
(3) cleaning costs may be minimized by reducing the consumption of cleaning solution by feeding a small quantity of a cleaning solution to the surface of the UV ray transmission tube and cleaning off scale, comprised of hardness components, etc. deposited on the surface of the UV ray transmission tube, by means of a scraper ring; and
(4) automation of the cleaning operation is facilitated thereby going with the desirable trend of equipment automation.
This invention achieves the above objectives by providing a UV irradiation apparatus in which a UV ray transmission tube(s), having internal UV ray lamp(s), is externally fitted with a scraper ring(s). UV ray irradiation of untreated water for sterilization, oxidative decomposition of organics, decomposition of harmful substances, etc. may be continued without interruption while cleaning UV ray transmission tube(s) by reciprocally sliding the scraper ring over the outer circumference surface of the said tube(s). The scraper ring(s) has a built-in cleaning solution chamber in contact with the outer circumference surface of said UV transmission tube(s) and is slidably and tightly fitted to said tube(s). A cleaning solution supply line communicates with said cleaning solution chamber to supply the cleaning solution.
This invention further provides a UV irradiation apparatus in which a UV ray transmission tube having an internal UV ray lamp(s) is externally fitted with a scraper ring(s) by fitting sealing material such as O-rings at a position on the surface of said UV ray transmission tube with which said scraper ring comes in contact and adjacent to the cleaning solution chamber(s) of the scraper ring(s).
This invention further provides a UV irradiation apparatus including means for reciprocally and repeatedly moving said scraper ring(s) over the circumference surface of the UV ray transmission tube(s). For example, said scraper ring(s) may be fitted to a movable frame which is fitted to a rotating screw which is externally fitted to said UV ray transmission tube and rotated forward and in reverse by means of a drive unit such as a motor.
Further features and advantages of the present invention will be appreciated by review of the following detailed description of the invention.